1. Field of the Invention
The present invention relates generally to modular integrated accessory mounting assemblies for combat weapons. More specifically, the present invention relates to an accessory mounting assembly, which includes a clamping assembly that provides adjustable spring tension to control the clamping force exerted against the firearm interface rail.
2. Background of the Related Art
As the field of combat and commercial weaponry expands, numerous add-on enhancements have become available for attachment to standard firearms, thereby significantly upgrading the capability of the firearm. Of particular interest in the area of combat weapons is the well-known M16/M4 weapon system (M16 and M4 are trademarks of Colt Defense, Inc.). The M16 has been in service for a number of years and will continue to be a popular rifle both in U.S. and foreign militaries for the foreseeable future. Generally, the M16/M4 weapon 2, as depicted in FIG. 1, includes a lower receiver 4, upper receiver 6, butt stock 8, and barrel 10.
The newer models of the M16/M4 weapons further include a mil-std 1913 dovetail rail 12 extending along the top of the upper receiver. This integrated receiver rail 12 provides a convenient mounting point for many types of enhancement devices such as scopes and other sighting devices.
In addition, many supplemental rail systems for M16/M4 weapons have also been created. As shown in FIG. 2, these supplemental rail interface systems for weapons 2 generally include an upper hand guard 14, a means 16 for securing the upper hand guard 14 to the weapon 2, a lower firearm accessory 18 (in most cases this is a lower hand guard), various optional rail segments, and in many cases, a sling swivel 20 for attaching a shoulder sling to carry the weapon 2. The upper hand guard 14 is generally semi-cylindrical in shape and has a forward end and a rearward end and a mil-std 1913 dovetail rail 22 extending longitudinally between the forward end and the rearward end.
The increasing development and refinement of laser sights, infrared lighting, visible lighting, night vision, and specialized scopes and magnifiers, and other accessories continues to drive the need for versatile and reliable integration systems that can support this important equipment and yet stand the test of rugged military use and abuse.
An existing attachment device is disclosed in U.S. Pat. No. 5,276,988, issued on Jan. 11, 1994 to the present applicant, the contents of the '988 patent being incorporated herein by reference. Generally, the prior art attachment assemblies include a main body 24 having a lower portion that is configured to engage the dovetail rail 22 found on most modern combat weapons 2 and an upper portion 26 that can take on a variety of configurations depending on the accessory that is to be mounted thereon. The lower portion of the attachment assembly has a first engagement member 28 extending downwardly along one side thereof for engaging one side of the dovetail rail 22. Further, a boss formation 30 is provided adjacent the side of the main body 24 to receive a clamping assembly 32 that is particularly suited to be releasably engaged with a second side of the dovetail rail such that the clamping assembly 32 cooperates with the first engagement member to retain the attachment assembly in its installed position on the dovetail rail 22. The clamping assembly 32 generally includes a foot portion 32A with a cam surface 32B to engage the angulated surface of the dovetail rail 12, a post extending upwardly through the boss formation 30 and a head portion 32C secured to the top end of the post and having actuator arm 32D to facilitate rotation of the foot portion 32A. The clamping assembly 32 further includes spring washers, which are captured between the bottom surface of the head portion 32C and the boss 30 (or a bushing within the boss) to provide a self-adjusting amount of spring tension as the clamping assembly 32 is rotated into engagement with the dovetail rail 22. These springs generally allow a limited, self-adjusted amount of biased vertical movement of the foot portion 32A relative to the boss 30 and the dovetail rail 22. Because the head portion 32C of the clamping assembly 32 is secured in a fixed position on the top end of the post, the spring are compressed by a fixed amount and therefore the force exerted by the foot portion 32A on the dovetail rail 22 was generally variable, but variable only within a certain range as determined by the initial spring tension. This small range of self-adjustment is critical in being able to accommodate the small dimensional variations in the dovetail rails 22 of various equipment manufacturers.
Further, when such devices are employed with sighting accessories it is critical that the alignment of the device be repeatable and reliable after several removal and reinstallation cycles. If the camming force is too loose, the sight cannot be reinstalled with a high degree of accuracy. Similarly, if the camming force is too great, rotation of the foot portion 32A can damage the dovetail rail 22 creating a sloppy fit over time.
Finally, despite the benefits of a fixed, self-adjusting range of spring tension provided by the prior art device, in certain environments, there is still a perceived need to adjust the range of the spring tension, for example if dovetail rails have excessive wear there may be a need to slightly increase the initial spring tension. However, there is also a desire to prevent the user of the weapon 2 from being able to adjust the tension without some type of restriction. Tighter is not better in these circumstances and over tightening can lead to damage to the rail 22 of the weapon 2. Accordingly, while a need for adjustment may be accommodated, it should be provided in a manner that accommodates all of the environmental variables while still allowing the accessory mount to be ruggedly attached to the rail 22. There is thus a struggle between the benefits of a fixed mounting so as to provide a fixed, self-adjusting range of spring tension, and the perceived need to be able to adjust the range of the spring tension.
Accordingly, there is a perceived need for a mounting assembly that allows for the releasable mounting of various accessories onto the standard dovetail rail 22 found on modern combat weapons 2 and that can be reliably mounted onto a dovetail rail 22 while including an actuator that includes the ability to adjust the spring tension that is exerted by the clamping foot.